Stereophonic sound system



Jan. 22, 1957 w. A. MUELLER STEREOPHONIC SOUND SYSTEM Filed April 6, 1953 INVENTOR Wm/mn 4 MUELLER 3.1K l I 3 STEREOPHONIC SOUND SYSTEM William A. Mueller, Los Angeles, Calif., assignor to Warner Bros. Pictures, Inc., Burbank, Califl, a corporation of Delaware Application April 6, 1953, Serial No. 347,109

5 Claims. (Cl. 179-1) This invention relates to stereophonic sound systems, and more particularly to stereophonic sound systems for use in exhibiting stereoscopic motion pictures.

With the advent of three dimensional motion pictures it becomes desirable to equip motion picture theaters with suitable stereophonic sound systems. These systems should include simplified control means for switching from the conventional sound system to the stereophonic sound system especially when three dimensional movies are to be shown. Also, because of the possibility of breakdown in the stereophonic systems, it is desirable to include in the control circuits suitable switching means for connecting in a complete composite photographic sound track without the necessity of interrupting the show.

It is a primary object of the present invention accordingly, to provide an improved stereophonic sound system suitable for installation in theaters exhibiting three dimensional motion pictures.

Another object is to provide an audio system for motion picture theaters including in combination conventional sound reproducing equipment and stereophonic sound reproducing equipment with suitable switch control means for changing over from one system to the other by means of a single control switch.

Another object of the invention is to provide in the control circuit a second single switch element for connecting in an emergency photographic sound track in the event of failure of certain components in the stereophonic system.

These and further objects of the invention are attained by providing a plurality of audio reproducing units, such as loudspeakers, along the side and rear walls or ceiling of an auditorium or motion picture theater and a second group of loudspeakers on the stage of the theater. Preferably, the auditorium loudspeakers extend substantially along the entire length and rear wall of the theater, there being provided speakers in the balcony as well as the orchestra. The stage loudspeakers include at least one unit or speaker at the lefthand side of the stage, a speaker at the center of the stage, and a speaker at the rlghthand side of the stage. adapted to be connected in conventional manner to a standard photographic sound track. This unit is also adapted, together with the left and right hand speakers on the stage, to be connected to left, center and right positioned stereophonic sound recordings respectively. The auditorium speakers are adapted for connection to a photographic sound track of selected music and sound effects, the latter sound track being used in cooperation with the three stage units for stereophonic efiects.

A switch control means is provided for simultaneously switching from the conventional sound system, which will ordinarily only employ speakers positioned substantially at the center of the stage, to the stereophonic system including the left and right stage speakers and the auditorium speakers. Suitable amplifiers and fading control circuits are employed to permit proper control of the stereophonics.

The center speaker on the stage is A better understanding of the invention will be had by referring to the single drawing which shows in schematic form a preferred embodiment of the invention.

In the drawing, the numeral designates a conventional motion picture theater auditorium including at least two motion picture projectors 11 and 12. In showing conventional motion pictures the projectors 11 and 12 are used alternately and are arranged to project the picture on a screen 13. In showing three dimensional films, an enlarged type screen is preferably used, usually extending across the entire stage 14 of the theater. The same screen of course can be used for conventional movies.

The sound system of the present invention comprises a plurality of auditorium loudspeakers including a bank of speakers 15, along the lefthand wall of the auditorium 10, a similar bank of speakers 16 along the righthand wall, and a set of speakers 15' and 16' along the rear wall. There are also provided on the stage 14 at least three speakers 17, 18 and 19 positioned to the left, center, and the right of the stage 14, respectively, as shown.

In exhibiting conventional motion pictures, the audio output signal from the photographic sound track from the projector 11 is fed through conductor 20, fading circuit 20, switch 21 when in the dotted line position, amplifier 22, conductor 23, through a ganged switch, conductor 24, and conductor 25 to the center stage loudspeaker 18. When the projector 12 is in operation its composite sound track may be connected to the center loudspeaker 18 by simply throwing the switch 21 to the solid line position as shown.

When exhibiting three dimensional motion pictures, which requires the simultaneous use of projectors 11 and 12, the projector 11 is generally provided with a complete composite photographic sound track including all of the stereophonic sound effects for emergency use, whereas the film in the projector 12 contains a sound track of only selected background music and sound effects. In switching from the conventional sound system to the stereophonic system, the switch 21 is thrown to the solid line position as shown. This switch will be maintained in this position throughout the entire show, but may at any time be thrown to the dotted line position to throw in the emergency composite sound track as will be described in detail later.

With the switch 21 in the proper position, the stereophonic sound system is placed in operation by closing either one of the stereo-sound selector switches 26 or 27 shown in the lower righthand portion of the drawing. These switches may be separately located for convenience, the closing of either one serving to connect power supplied to the terminals 28 across a solenoid coil 29 to actuate the ganged switch 30. Indicating lights 31 and 32 may be provided in the switch circuits respectively to inform an operator when the switch is properly closed.

With the ganged switch closed, the source of seleeted music and sound effects from projector 12 passes through a conductor 33, fading circuit 33, switch 21, amplifier 22, conductor 23, and conductor 34 to two branch conductors 35 and 36. The conductor 35 applies this sound to the rear wall speaker 16' and the righthand bank of loudspeakers 16, while the conductor 36 applies the same signal to the rear wall speaker 15 and the lefthand bank of loudspeakers 15. The fading circuits 20 and 33 are conventional and may comprise simple variable resistance pads.

It will be noted that upon actuation of the ganged switch 30, the connection of conductor 23 to conductor 24 is opened and the former sound signal on the center loudspeaker 18 on the stage is removed. Simultaneously connected into the circuit are left position, center position, and right position stereophonic sound recordings 37, 38 and 39 respectively, through faders 4d, 4?. and 42.; amplifiers 43, 44 and 45; and conductors 45, 25, and 47 to the left, center, and right stage loudspeakers i7, 18 and 19. Thus, in accordance with the motion picture being shown, when the sound is supposed to be coming from the lefthand portion of the screen 13:, the loudspeaker 17 will dominate. As the sound source in the picture moves across the screen 13 as in the case of a train, automobile, or person walking, the center speaker 18 and right-hand speaker 19 become progressively dominant, to audibly simulate the proper position of the sound source as visually represented. This is accomplished automatically by the separate sound recorders 37, 38 and 39.

While three separate recording in three separate heads 37, 38 and 39 have been illustrated, it is to be understood that these recordings may be combined on a single tape or film 'having three separate sound tracks.

Should there be a breakdown in the stereophonic sound system such as might occur in one of the recordings 37, 38, or 39, the complete composite photographic soundtrack in projector .11 can be immediately connected to the center screen loudspeaker by simply opening switch 26 or 27 and throwing the switch 21 to the dotted line position. It should be noted that if desired, the center loudspeakers may be used for reproducing a conventional sound track from either of the projectors ill or 12 when these projectors are employed for exhibiting conventional motion pictures.

By the present arrangement it is thus seen that a complete stereophonic sound system may be readily placed in operation and the conventional sound system discon nected simultaneously by operation of a single control switch. Furthermore, in the event of an emergency resulting from a breakdown of some component of the stereophonic system, a complete composite soundtrack may readily be connected to the auditorium speakers by simply throwing switch 21 and opening switch 26 or 27 It is the belief of many that stereoscopic motion pictures will become increasingly used in the motion picture industry, possibly largely replacing the present fiat" picture-s. Stereophonic sound systems will also become increasingly the vogue in the industry. Like changes in any other industry, such a transition i best made with a minimum of expense and dislocation of existing practices and hasty scrapping of existing equipment. The invention set forth herein does muchto promote the ease and economy of the transition.

Thus it makes possible a five-way use of stereoscopic film-s and the sound recordings used in conjunction therewith.

1. A theater equipped with two standard projectors, and a standard sound system, may alternately in the conventional manner use in its projectors successive reels of that one of the right and left hand stereoscopic films which has the composite sound track thereon (the lefthand one as set forth in this drawing and description), resulting in the standard production of a flat picture with a single, complete sound accompaniment. In such a use, the switch 21 would be thrown from one position to the other with the showing of each new reel.

2. If the theater is thus equipped and the desire is to show stereoscopic pictures, this may be done by running one of the two stereoscopic films with a composite sound track in one projector with the switch 21 thrown to connect the sound track of this film to the single speaker behind the screen, the other sound track with background and sound efiects on the other stereoscopic film 'being disconnected and without effect.

In cases 1 and 2, if the stereophonic speakers and positional sound recording heads are installed gang switch 24 must be in its upper position.

3. Ifthe theater is equipped with speakers as herein described and arranged for connection by the switches in the manner set forth, giving stereophonic sound results, but the desire is to show a flat picture with such stereophonic sound, both projectors are alternately operated with stereoscopic films having background sound effects, switch 21 is thrown alternately to the right and lefthand positions and switch 30 is thrown to the lower position, the three sound recording from heads 3'7, 38 and 39 being thus brought into action.

4. If both stereophon'ic and stereoscopic effects are desired, the two projectors are run simultaneously showing respectively the right and left stereoscopic films carrying composite and background sound tracks respectively, with the switch 21 in right hand position and switch 24 in its lower position.

5. If both stereoscopic effects and a modified, simpli fied stereophonic sound effect are desired, the equipment and connections shown in the drawing may be supplemented to provide an inexpensive means for operating two projectors, with right and left hand stereoscopic films for stereoscopic effects, with a composite soundtrack on the lefthand film, for example, with electrical connections to a single central stage speaker, and with a sound track of background sound effects on the other film with connections to the auditorium speakers on the sides and at the rear of the auditorium. To accomplish this a switch 50 is provided which in its full line position as shown on the drawing operates to disconnect, and in its dotted line position, to connect the soundtrack on the righthand film shown in projector 12 with the auditorium speakers by conductor 33, conductor 51, amplifier 52, conductor 53, and conductors 3S and 36 to the right and left hand auditorium speakers respectively. When the switch 50 is thrown from its full line to its dotted line position the arm 54 moves leftward to throw the switch 21 from its right to its left hand position, connecting the soundtrack of the film which is being run through projector 11 to the central stage speaker 18 by the conductors 23, 24 and 25, as has been previously described. This arm 54 moves the switch 21 by means of a forked terminal 55 constructed to move the switch 21 leftward when the switch 21 is in the right hand position but which does not retract switch arm 21 from its lefthand dotted line position when the switch arm St is moved from its lefthand dotted position to its righthand full line position.

Since in this simplified form of the invention, the left, center and right recording heads 37, 38, and 39, and the gang switch 39 are not in operation, means must be pro vided for automatically disconnecting them. This is accomplished by means of a circuit 57 connecting the two portions 58 and 60 of the common return conductor of the relay 29 of the gang switch 36) with a switch 56 which by means of an extension 55 of the arm 54- opens the circuit 57 when the switch 50 is in its lefthand dotted position, and closes it when the switch 5th is in its righthand full line position. When, therefore, the sound tracks on the films in projectors 11 and 12 are connected to the central stage speaker and the auditorium speakers respectively in the manner just described, the recording heads 37, 38 and 39 cannot be operated by throwing either of the switches 26 and 27 to pull down the gang switch 30 to its lower position.

If the theater is not equipped with stereophonically positioned stage speakers nor with the left, center and right sound recording heads, nor with the switch 36 or the operation thereof, conductor 20 may be permanently connected to conductor 23 across the switch 21 and circuit 57 may be entirely omitted. in that event we have only a central speaker connected permanently to the sound track of the film of the lefthand projector lit and the composite soundtrack on the film of projector 12 connected permanently to the auditorium speakers.

Various modifications of the present invention will occur to those skilled in the art. For example, while only six loudspeakers have been shown on each side of the theater, three of these on each side being preferably in the orchestra and another three on each side being preferably in the balcony, and two rear wall speakers, any number of loudspeakers may be used. Moreover, any desired number of loudspeakers may be used on the stage, the three speakers shown being merely illustrative. Also the center stage speaker may be behind the screen and the left and right stage speakers may be placed laterally beyond the two ends of the screen respectively on either side of the auditorium. The invention therefore is not to be thought of as limited to the precise embodiment disclosed.

I claim:

1. In a sound system for use in an auditorium having a stage at one end, the combination comprising: a plurality of stage loudspeakers including at least three loudspeakers positioned to the left, center and right of said stage; a complete composite photographic sound track; stereophonic sound means including left, center and right positioned recordings; and switch means operable in one position to connect said composite photographic sound track to the center loudspeaker on said stage, and operable in the other position to disconnect said composite sound track from the center loudspeaker and connect said left, center and right positioned recordings to the left, center and right positioned stage loudspeakers respectively.

2. The combination of claim 1 including a plurality of auditorium loudspeakers on each side of the auditorium and an audio source of selected music and sound effects said switch means being constructed to connect said auditorium loudspeakers to said source of selected music and sound effects when said switch means is in said other position.

3. In a motion picture sound system for use in an auditorium having a stage at one end, the combination comprising: a composite photographic sound track; an audio source of selected music and sound effects; stereophonic sound means including at least a left position sound recording, a center position sound recording, and a right position sound recording; a plurality of audio reproducing units on each side of said auditorium; at least left position, center position, and right position audio reproducing units on said stage; and means connecting said audio reproducing units with said sound track, audio source, and stereophonic sound means ineluding: a selector switch adapted in one position to connect said sound track to said center stage unit and in a second position to connect said audio source to said center stage unit, and further ganged switch means adapted simultaneously to disconnect said audio source from said center stage unit and connect it to all of said auditorium units, and connect said left, center, and right positioned recordings of said stereophonic sound means to said left, center, and right stage units respectively.

4. In a stereophonic sound system, the combination comprising: a complete composite sound source, an audio source of selected music and sound effects; left, center and right positioned sound recordings; a plurality of auditorium loudspeakers; a plurality of stage loudspeakers positioned on the left, center, and right positions of the auditorium stage; and a control circuit including: means for selectively connecting said composite sound source and said audio source to said center positioned stage loudspeakers and to said auditorium loudspeakers; and means for connecting simultaneously with the selected connection to the auditorium loudspeakers, the left, center and right positioned sound recordings to the left, center and right positioned stage loudspeakers, respectively.

5. In a sound system for use in an auditorium having a stage at one end, the combination comprising: a stage loudspeaker; a plurality of auditorium loudspeakers distributed on each side of the auditorium; two projectors with left and right hand stereoscopic films therefor with a complete composite soundtrack on the one film and a soundtrack of a selected background music and sound effects on the other film; means for selectively connecting said composite sound track to said stage loudspeaker and to said auditorium loudspeakers; and means for selectively connecting said soundtrack of selected background music and sound effects to said stage loudspeaker and to said auditorium loudspeakers.

References Cited in the file of this patent UNITED STATES PATENTS 1,589,139 Foley June 15, 1926 1,950,011 Scheibell Mar. 6, 1934 1,990,388 Lootens Feb. 5, 1935 2,060,204 Hammond Nov. 10, 1936 2,101,121 Wixon Dec. 7, 1937 2,298,618 Garity et al. Oct. 13, 1942 

